Transducers for generating vibrations in liquids



March 29, 1960 w. CAMP ETAL 2,930,913

TRANSDUCERS FOR GENERATING VIBRATIONS IN LIQUIDS Filed Oct. 2, 1957 2Sheets-Sheet 1 C 2 /5 fi ,6 +11 a /6 INVENTORS L. W. Gfl MP J. P. 0NE/LL BY ATTORNEY March 29, 1960 L. W. CAMP ETAL TRANSDUCERS FORGENERATING VIBRATIONS IN LIQUIDS Filed Oct. 2, 1957 2 Sheets-Sheet 2INVENTORS L. w. CAMP J. P. O'NEILL ATTORNEY United States PatentTRANSDUCERS FOR GENERATING VIBRATIONS IN LIQUIDS Leon W. Camp, SantaMonica, and James P. ONeill,

Sunland, Calif., assignors to Bendix Aviation Corporation, NorthHollywood, Calif., a corporation of Delaware Application October 2,1957, Serial No. 687,725

20 Claims. (Cl. 310-26) This invention relates to electromechanicaltransducers for generating sonic waves in fluid media, the term sonic,as here used, including waves of frequencies above 'audibility, as wellas those within the audible range.

An object of the invention is to provide transducers of satisfactoryefiiciency that can be manufactured relatively cheaply.

Another object is to provide a satisfactory and inexpensive-motion-translating structure for coupling theelectromechanically-responsive element of a transducer to the workingface thereof that is in contact with. the fluid medium.

Another object is to provide simple and effective structures forsupporting transducers in a wall of a tank.

. Another object is to provide a simple and effective structure forpreventing lateral vibration of the laminations of a magnetrostrictivetransducer.

Other more specific objects and features of the invention will becomeapparent from the following description.

The invention has to do with that type of sonic transducer in which anelectromechanically-sensitive body has its vibratile working facecoupled by a mechanical motion-translat-ing structure to a diaphragm incontact with a working liquid'medium, as distinct from those in whichtheworking face itself is in contact with the liquid. Various advantagescan be obtained by the addition of a motion-translating structure andseparate diaphragm, one of which is to obtain a better impedance matchwith the liquid. A motion-translating structure for this purpose isdisclosed in US. application Serial No. 556,991 of J. P. ONeill, filedJanuary 3, 1956, that consists of an elongated hollow body defining a.closed, gas-filled cavity, which body is rigidly joined to anelectromechanicallyresponsive element at one end, the other endconstituting the working face in contact with the liquid medium. Thatmotion transducer is highly efiicient and satisfactory in performance,but is relatively expensive to construct.

The present invention resides in motion transducers having many of thedesirable operating characteristics of the prior construction, but ofsimpler constructions that are substantially cheaperto manufacture. Oneembodiment of the present invention comprises a hollow cylindricalmidsection interconnecting the base and head portions, withperipherally-spaced longitudinal grooves in the inner or outer surface.The midsection thereby consists of an integral hollowtubular memberhaving a plurality of longitudinal sections of different thickness, thethinner sections being at the grooves and the thicker sections beingbetween the. grooves. The combination of thick and'thin sections reducesundesired lateral vibration to a substantial degree relative to thedesired longitudinal vibration. The structure is relatively cheap tomake, because it can be produced by simple machining operations from asolid body, or can be fabricated from standard tubing.

Another embodiment of the invention comprises a hollow conicalmidsection with a peripheral rib intermediate 2,930,913 Patented Mar.29, 1960 ice the ends, the rib greatly reducing the magnitude ofvibrations in the undesired lateral mode.

It is desirable that transducers mounted in the wall of a tank bereadily replaceable, either individually or in groups. This isaccomplished by a modular construction.

The foregoing, together with other lesser improvements, will becomeapparent from the following detailed description with reference to thedrawing, in which:

Fig. l is an elevation view, partly in section, of an apparatusincorporating the invention for cleaning the under side of sheets movinghorizontally through a tank.

Fig. 2 is a plan view taken in the plane IIII of Fig. 1.

Fig. 3 is a lower end view of one transducer element taken in the planeIIIIH of Fig. 1.

Fig. 4 is a detailed vertical section through one of the units of Fig.1.

Fig. 5 is an elevational view, partly in section, of one of themotion-transforming members in Fig. 1.

Fig. 6 is a cross-section taken in the plane VIVI of Fig. 5.

Fig. 7 shows an alternative construction to that of Fig.5.

Fig. 8 is a cross-section taken in the plane VIII-VIII of Fig. 7.

Fig. 9 is a vertical sectional view showing another alternativeconstruction.

Fig. 10 is a vertical sectional view showing still another alternativeconstruction.

Referring first to Figs. 1 and 2, a sheet 15 to be cleaned is adapted tobe moved through liquid in a tank while supported at a fixed level byrollers 16. Only the bottom wall 15 of the tank is shown.

Detachably mounted over a rectangular aperture 17a in the bottom wall 17is a transducer module consisting of a mounting plate 18 carrying aplurality of transducer units 19 arranged in staggered relation in tworows extending the full width of the sheet 15, so that each portion ofthe latter passes over a transducer and is subjected to intense sonicwaves generated in the liquid by the transducers.

Each transducer unit 19 comprises a longitudinally expansible andcontractible electromechanically-responsive body 20 having a front endface 21 of substantial area joined to the rear end 22 of amotion-transforming member 23 having a front working face 24 ofsubstantial area. For convenience, this end face 24 will hereafter bereferred to as the diaphragm. The member 23 and the body 20 are joinedat their faces 22 and 21, respectively, by brazing, soldering, or in anyother suitable way.

In the construction shownin Fig. l, the assembly of the body 20 and themember 23 are supported by a mounting ring 26 having an aperture largerthan the diameter of the member 23 with a rubber ring 27 filling thespace therebetween and bonded to the ring 26 and the body 23. Thisprovides a watertight connection between the ring and the member 23, andat the same time permits longitudinal vibration of the member 23relative to the ring 26. The ring 26 fits in an aperture 18a in theplate 18 and is sealed with respect thereto by an O-ring 28 'rnounted ina groove in the external surface of the ring 26. A flange 26b on theupper end of the ring 26 rests on the plate 18 and supports the ringwith respect to the netostrictive vibrator, as shown in Fig. l, andconsists of V a stack of generally U-shaped laminations so that the bodyas a whole has two downwardly depending legs which extend through apotted coil assembly 31, which is supported by screws 32 from the ring26. As best shown in Fig. 4, the coil assembly 31 has apertures ofsuflicient size to permit the legs 28a and 28b of the transducer toextend therethrough without contacting the coil assembly.

It has been general practice in the construction of laminatedmagnetostrictive drivers of the'type here disclosed to bond thelaminations together with some adhesive. However, it is found that inpractice when such transducers are operated under heavy duty, the forcesand the heat usually separate the laminations, causing them to bow andvibrate. in accordance with the present invention, such bowing andvibrating is prevented, and the bonding made unnecessary, by placing aU- shaped spring clip 35 over each transducer leg. As best shown in Fig.3, each clip 35 has a broad base 35a extending across the edge portionsof all the laminations, and curved leg portions 35b which bear againstthe outer faces of the opposite laminations in the stack. Apertures 350(Fig. l) are preferably cut out of the clips to facilitate circulationof the ambient cooling fluid or cooling gas or liquid to thelaminations. As best shown in Fig. 4, each clip 35 is supported inposition by an integral outwardly extending lug portion 35d at the upperend, which engages the upper face of the potted coil assembly 31. Theclip 35 vibrates with the transducer leg on which it is mounted, andnormally the lug 35d rides slightly above the potted coil 31.

With a structure as so far described, the entire module can be removedfrom the tank with the plate 18, or transducers can be removedindividually. Thus, any individual transducer can be removed from theinside of the tank by'simply removing the screws 31 that hold it to theplate 18, and lifting the assembly consisting of the body 28, the member23, and the ring 26 away from the plate 18. The coil 31 also is a partof the assem: bly and is of such size as to pass through the aperture18a.

A polarizing magnet 37 is positioned between the two legs 28a and 20b ofeach magnetostriction element and is supported by a U-shaped clip 38secured by bolts 39 to the potted coil.

The particular construction of the motion-transforming member 23 isshown in Figs. 5 and 6. It is solid at its base, but is hollowthereabove, having a cylindrical wall 23a extending through the majorportion of its length. The upper end or head 23b is preferably formedseparately and joined to the upper end of the wall 23a by brazing orwelding. Desirably, the head 23b, in a brazed assembly, has a downwardlydepending skirt 230 in which the upper end of the wall 23a is atight-pressed fit. The interior of the head 23b desirably has crossed,downwardly-depending webs 23d to stiffen it, so that the outer face 24vibrates as a solid element in a single mode.

The construction involving the cylindrical wall 23a is highly desirablefrom a manufacturing standpoint, since it can be fabricatedinexpensively. However, simple hollow cylindrical structures have atendency to vibrate undesirably in lateral modes, and because of thisundesirable characteristic much more complicated structures have beenresorted to in the past. In accordance with the present invention, ithas been found that by forming longitudinal grooves 23:; in the thincylindrical wall 23a, so that the latter consists of a plurality oflongitudinal sections integral with each other and each of uniformthickness longitudinally, but one set of alternate sections being ofgreater thickness than the intervening section, the fundamental resonantfrequency of lateral vibration is reduced to a suflicient extent to makethe device practicable. The grooves 23e provide thin longitudinalsections 23 joining the thicker sections 23g.

Fig. 7 shows a slight modification of the structure of Fig. 5 in thatthe grooves 24a are formed in the inner surface of the cylindrical wall24a, instead of in the outer surface. Both constructions are equallyefiicient, and the choice depends on which is easier to manufacture. Ineach case, the resultant thin sections joining thicker sections serve tosuppress the lateral vibratlons.

The head 24b in Fig. 7 is identical with that in Fig. 5, except that anouter hard corrosion-resistant wear plate 48 is attached to the outerend of the head and constitutes the working face 24 of Figs. 1 and 5.This wear plate 4i) may be of some hard corrosion-resistant material,such as stainless steel, and can he joined to the head 241) by an epoxycement indicated at 41. It is found that such cement satisfactorilyresists the vibration forces involved, and yet permits removal of theWear plate 40 and substitution of a new one.

Fig. 7 also shows an alternative mounting of the transducer in the plate18a, which corresponds to the plate 18 of Fig. 1, but is of sheet metalconstruction having drawn apertures therein which provide integralcylindrical extensions, or flanges, 18b. Each drawn flange 18b providesan inner cylindrical face in which a cylindrical piston face 2411 on thelower end of the member 24 is slidably fitted. The face 2411 has agroove 24] containing an O-ring 24k which effects a fluid seal betweenthe piston surface 24/1 and the cylinder surface 180. A flange 241 isprovided at the upper end of the piston surface 24h to limit downwardmovement of the transducer with respect to the plate 18a, and a snapring 24m mounted in a groove 2411 in the piston face 24h limits upwardmovement of the transducer with respect to the plate 18a. The distancebetween the lower edge of the flange 2 M and the upper edge of the snapring 24m is slightly greater than the length of the cylindrical section180, so that when the transducer is vibrating, it assumes a position inwhich the flange 241 is slightly above the plate 18a, and the ring 24mis slightly below the lower end of the flange 18b. The mountingstructure described with reference to Fig. 7 is substantially simplerthan that disclosed in Fig. 1, and is generally satisfactory in service.

Fig. 9 discloses an alternative construction of motiontransformingmember in which the thickness of the peripheral wall 50 is slightlytapered in thickness longitudinally, so that it is thinner at its upperend than at its lower end. It is found that'this construction tends toreduce the magnitude of the undesired lateral vibrations and may beemployed in place of the grooved construction shown in Figs. 5 and 7.However, it is somewhat more expensive to manufacture.

Still another alternative construction is disclosed in Fig. 10, in whichthe wall 51 is not only tapered as to thickness, but as to diameter,expanding from a small diameter at the lower end to a greater diameterat the upper end. This construction has the desirable characteristics ofproviding a larger head 52 relative to the size of theelectromechanically-rcsponsive body '56 that drives it. Such conicalstructures have been tried before, but have been found to be verycritical as to their dimensions in order to prevent excessive lateralvibration.

It has been found in accordance with the present invention that thesevibrations can be greatly reduced by providing an integral peripheralrib 51a on the wall 51. This stiffening rib is located at thelongitudinal point where the greatest lateral vibrations would occur ifit were not present. In effect, it constitutes a thickening of the walland may be placed either on the outside, as shown, or

on the inside. It is usually easier in manufacture to produce it on theoutside.

Although for the purpose of explaining the invention. certain particularembodiments thereof have been shown.

W v fl s m e a q siti ernl r XPFiP and contractibleelectromechanically-responsive body having a front end face ofsubstantial area; a diaphragm longitudinally spaced from said end faceand having a front working face of substantial area at least as large assaid end face; a hollow motion-transforming member interposed betweenand interconnecting said body and daiphragm and comprising a solid basejoined to said front face and a continuous peripheral wall joined to'andextending between the peripheral portion of said solid base and theperipheral portionof said diaphragm and defining a closed cavitycontaining a gas of small acoustic impedance relative to that of aliquid contacting said working face of the diaphragm, said continuousperiph eral wall being curved in peripheral direction and straight inlongitudinal direction and being of uniform thickness in one of saiddirections and varying in thickness in the other of said directions;said motion-transforming member constituting the sole suppont for saiddiaphragm and the diaphragm being substantially rigid whereby itvibrates in a single mode with the adjacent end of said member, and thecross-sectional area of said cavity being large relative to that of thesaid peripheral wall whereby the major area of the diaphragm isjuxtaposed to said cavity.

2. Apparatus according to claim 1 in which said peripheral wall variesabruptly in thickness in the other of said directions.

3. A transducer for high-frequency compressional WaJVBS in fluidscomprising: a longitudinally expansible and contractibleelectromechanically-responsive body having a front end face ofsubstantial area; a diaphragm longitudinally spaced from said end faceand having a front working face of substantial area; a hollowmotiontran-sforming member interposed between and interconnecting saidbody and diaphragm and comprising a solid base joined to said front faceand a continuous peripheral wall joined to and extending between saidsolid base and said diaphragm and defining a closed cavity containing agas of small acoustic impedance relative to that of a liquid contactingsaid working face of the diaphragm; said continuous peripheral wallbeing curved in peripheral direction and straight in longitudinaldirection and comprising a plurality of longitudinal sections integralwith each other, each section being of uniform thickness longitudinally,but one set of alternate sections being of greater thickness than theintervening sections, whereby the fundamental resonant frequency oflateral vibration of said wall is modified relative to the fundamentalresonant. frequency of longitudinal vibration of said transducer.

4. Apparatus according to claim 3 in which said intervening sections aresubstantially narrower than said one set of sections.

5. A transducer for high-frequency compressional waves in fluidscomprising: a longitudinally expansible and contractibleelectromechanically-responsive body having a front end face ofsubstantial area; a diaphragm longitudinally spaced from said end faceand having a front working face of substantial area; a hollowmotiontransforming member interposed between and interconnecting saidbody and diaphragm and comprising a solid base joined to said front faceand a continuous peripheral wall joined to and extending between saidsolid base and said diaphragm and defining a closed cavity containing agas of small acoustic impedance relative to that of a liquid contactingsaid working face of the diaphragm; said continuous peripheral wallbeing substantially cylindrical in shape and of uniform thickness in oneof said directions and varying thickness in the other of saiddirections.

6. Apparatus according to claim 3 in which the faces of all saidsections are flush with each other in one surface of said peripheralwall, and the opposite faces of 7. Apparatus according to claim 1 inwhich said peripheral wall is of uni-form thickness in said peripheraldirection and tapers in said longitudinal direction from a maximumthickness adjacent said body to a minimum thickness adjacent saiddiaphragm.

8. Apparatus according to claim 7 in which one surface of saidperipheral wall is substantially cylindrical and the other isfrustoconical.

9. A transducer for high-frequency compressional Waves in fluidscomprising: a longitudinally expansible and contractible.electromechanically-responsive body having a front end face ofsubstantial area; a diaphragm longitudinally spaced from said end faceand having a front working face of substantial area; a hollowmotiontransforming member interposed between and interconnecting saidbody and diaphragm and comprising a solid base joined to said front faceand a continuous peripheral wall joined to and extending between saidsolid base and said diaphragm and defining a closed cavity containing agas of small acoustic impedance relative to that of the liquidcontacting said working face of the diaphragm; said continuousperipheral wall being of uniform thickness in said peripheral directionand tapering in longitudinal direction from a maximum thickness adjacentsaid body to a minimum thickness adjacent said diaphragm and having aperipheral rib intermediate its ends.

10. Apparatus according to claim 9 in which said peripheral wall expandsfrom a minimum diameter adjacent said body to a maximum diameteradjacent said diaphragm.

11. Apparatus of the type described comprising: a wall constituting aliquid barrier and having an orifice portion defining a cylindricalpassage extending therethrough; an integral vibrator comprising avibration-translating member extending through said passage with a frontend beyond the liquid side of said wall, and a rear electromechanicaldriver positioned beyond the other side of said wall; saidvibration-translating member including a portion fitting pistonwise influid-sealing relation in said cylindrical passage and means forlimiting axial movement in each direction of said portion of said memberin said passage.

12. Apparatus according to claim 11 in which said last-mentioned meanscomprises a shoulder on said member at the liquid end of said passageand a detachable stop element on said member at the other end of saidpassage.

13. Apparatus according to claim 12 in which said stop element is a snapring in a groove in said member.

14. Apparatus according to claim 11 in which said portion of saidtranslating member comprises a mounting 7 ring having an outerperipheral surface in said fluidsealing relation with said cylindricalpassage and an inner peripheral surface juxtaposed to said translatingmember, and a rubber ring interposed between and bonded to saidjuxtaposed surfaces of said translating member and mounting ring foryieldably supporting said translating member for longitudinal vibrationwith respect to said mounting ring.

15. Apparatus according to claim 14 in which said driver comprises amagnetostriction element; a winding assembly surrounding saidmagnetostriction element out of contact therewith; and means detachablysupporting said winding assembly from said mounting ring; whereby saidvibrator mounting ring and winding assembly are removable as a unit fromsaid wall.

16. Apparatus according to claim 11 in which said wall is of sheet metalhaving an aperture therein and said orifice portion consists of anannular sheet metal ring surrounding said aperture and integral withsaid wall and extending from said other side of said wall.

17. A transducer having a laminated magnetostrictive core and springclamping means pressing said laminations together to prevent relativelateral motion therebetween.

18. Apparatus according to claim 17 in which said spring clamping meanscomprises a U-shaped clip having a base portion adapted to extend acrossthe edge portions of said laminations and leg portions bearing againstthe outer faces of'the outermost laminations.

19. Apparatus according to claim 18 including an energizing coilstructure surrounding said laminations and said spring clamp, means forsupporting said coil structure independently of said magnetostrictionelement, and a lug extending from one end of said clip into engagementwith a portion of said coil structure for supporting said clip againstlongitudinal displacement.

20. Apparatus according to claim 18 in which said U-shaped clip elementshave perforations therein permitting circulation of cooling fluid tosaid laminations.

References Cited in the file of this patent UNITED STATES PATENTS FayJune 7, Wood et al. Apr. 6, Smith Sept. 10, Hayes Nov; 26, Fryklund Feb.28, Mason et a1 Oct. 30, Bourgeaux Nov. 4, Calosi et al. May 29,Thatcher. Dec. 18,

FOREIGN PATENTS Great Britain Jan. 13,

Germany Nov. 12,

